§6 
Molls'^ System Crystallography 
might be sufficiently determined. In these circumstances;, it 
would be found that this individual belongs to the genus iron- 
pyrites ; it might also be hence concluded that its form is not 
rhomhoidal ; but whether it be hexaedral or prismatic iron-py- 
rite% would remain undetermined. Any mineral which admits 
of the preceding three characteristics being observed, is, by 
means of this system of characters, an object of natural historical 
determination. This mode of determination is named the imme- 
diate mode. 
1^. Mediate determinatio7i.—^1dvit all minerals are not found 
to allow the preceding three characteristics to be estimated, with 
the required degree of precision. The form is sometimes not 
to be discovered, even by applying the means previously ex- 
plained. (i. 65.) Such individuals, therefore, do not admit an 
immediate determination ; and the mineralogist, in regard to 
them, finds himself in the same situation as the botanist, when a 
vegetable that does not flower is presented to him. In this case, 
the botanist compares the unblossoming plant with one that does 
blossom ; and practice has taught him, how far this comparison 
must be carried to produce a sure result. The mineralogist 
proceeds in exactly a similar manner. He determines the indi- 
vidual not capable of immediate determination, by means of 
Others^ which he forms into a series, placing the given mineral 
at the end. This mode of determination is named the mediate. 
It depends on the transitions^ and has already been so frequent- 
ly applied, that it were superfluous to say more on the subject. 
1^. ’Beginners ought first to engage with the immediate^ then 
with the mediate mode (f determination. — Every natural history 
system, with its dependencies, is first intended for the tyro in na- 
tural history. When a beginner has acquired an acquaintance 
with the characteristics, and some dexterity in the observation 
of cleavage ; he ought diligently to employ himself in the exami- 
nation of such minerals as are immediately determinable. Of 
this kind are those among the solid fossils, in which form (be 
it either the external or the cleavage form,) hardness and spe- 
cific gravity are each capable of being estimated,— presup- 
posing, with regard to the first of these characteristics, that 
the species appear in regular forms. For when this is not the 
case, as in coals, &c., the form is also at the same time unne- 
